Nitrogen generators and stations are stationary or mobile air-to-nitrogen production complexes.
Read Pritish Halder below article to understand the concept of Nitrogen gas and its separation method.
The adsorption gas separation process in nitrogen generators is based on the phenomenon of fixing various gas mixture components by a solid substance called an adsorbent. This phenomenon is brought about by the gas and adsorbent molecules’ interaction.
Pressure swing adsorption technology
The technology of air-to-nitrogen production with the use of adsorption processes in nitrogen generators is well studied and widely applied at industrial facilities for the recovery of high-purity nitrogen.
The operating principle of a nitrogen generator utilizing the adsorption technology is based upon the dependence of the adsorption rates featured by various gas mixture components upon pressure and temperature factors. Among nitrogen adsorption plants of various types, pressure swing adsorption (PSA) plants have found the broadest application world-wide.
The system’s design is based on the regulation of gas adsorption and adsorbent regeneration by means of changing pressures in two adsorber–adsorbent-containing vessels. This process requires constant temperature, close to ambient. With this process, nitrogen is produced by the plant at the above-atmospheric pressure, while the adsorbent regeneration is accomplished at below-atmospheric pressure.
The swing adsorption process in each of the two adsorbers consists of two stages running for a few minutes. At the adsorption stage oxygen, H2O and CO2 molecules diffuse into the pore structure of the adsorbent whilst the nitrogen molecules are allowed to travel through the adsorber–adsorbent-containing vessel. At the regeneration stage the adsorbed components are released from the adsorbent vented into the atmosphere. The process is then multiple repeated.
Gas separation concept
The operation of membrane systems is based on the principle of differential velocity with which various gas mixture components permeate membrane substance. The driving force in the gas separation process is the difference in partial pressures on different membrane sides.
Structurally, a hollow-fiber membrane represents a cylindrical cartridge functioning as a spool with specifically reeled polymer fibers. Gas flow is supplied under pressure into a bundle of membrane fibers. Due to the difference in partial pressures on the external and internal membrane surface gas flow separation is accomplished.
Applications of nitrogen generators
1)Food and beverage industries: The moment food or beverages are produced, or fruits and vegetables harvested, an aging process kicks in until the complete decay of the products. This is caused by chemical reactions with oxygen, bacteria and other organisms. Generators are used to flood the products with N2 that displaces the oxygen and prolongs the product lifetime significantly because these organisms cannot develop. Furthermore, chemical degradation of food caused by oxidation can be eliminated or stopped.
2)Analytical chemistry: Nitrogen generators are required for various forms of analytical chemistry such as liquid chromatography–mass spectrometry and gas chromatography where a stable and continuous supply of nitrogen is necessary.
3)Aircraft & motor vehicle tires: Although air is 78% nitrogen, most aircraft tires are filled with pure nitrogen. There are many tire and automotive shops with nitrogen generators to fill tires. The advantage of using nitrogen is that the tank is dry. Often a compressed air tank will have water in it that comes from atmospheric water vapor condensing in the tank after leaving the air compressor. Nitrogen maintains a more stable pressure when heated and cooled as a result of being dry and doesn’t permeate the tire as easily due to being a slightly larger molecule (155 pm) than O2 (152 pm).
4)Chemical and petrochemical industries: The primary and very important application of nitrogen in chemical and petrochemical industries is the provision of inert environment aimed at ensuring general industrial safety during cleaning and protection of process vessels. In addition, nitrogen is used for pipelines pressure testing, chemical agents’ transportation, and regeneration of used catalysts in technological processes.
5)Electronics: In electronics, nitrogen serves to displace oxygen in the manufacture of semi-conductors and electric circuits, heat treatment of finished products, as well as in blowing and cleaning. The most common uses in electronics are in the soldering process. Specifically Selective, Reflow, and Wave Soldering equipment.
6)Fire Protection: The fire protection industry uses nitrogen gas for two different applications – fire suppression and corrosion prevention. Nitrogen generators are used in hypoxic air fire prevention systems to produce air with a low oxygen content which will suppress a fire. To prevent corrosion, nitrogen generators are used in place of or in conjunction with a compressed air system to provide supervisory nitrogen gas in place of air for dry pipe and pre-action fire sprinkler systems.